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User Manual 380 of 562 V 1.0
2021-08-25
XDPP1100 technical reference manual
Digital power controller
Central processing unit subsystem
15.3.3.1
Reset sources
The CPUS supports multiple reset sources:
•
External reset
•
CPUS_EN reset
•
SW_PWDN reset
•
WDT reset
•
CPU system reset
•
Soft reset
•
Peripheral modules reset
The external reset signal (RSTN) is used to generate the root CPUS signal (II_RSTN), the PWRONB signal, to put
the RAM and ROM in power-down, and the FREEZE clock gating signal, to gate the primary input source clock,
hosc_clk (
HW_PWD and SW_PWD signals are able to trigger, internally to CPUS, a logic reset state (II_RSTN), with RAMs
and ROM in power-down (PWRONB) and input clock hosc_clk gated (FREEZE).
In particular, to guarantee proper hold-time delay to PWRONB signal deassertion, the II_RSTN signal
deassertion is stretched for at least 500 ns (more than 50 hosc_clk cycles at 100 MHz).
Figure 104
Reset generation scheme
RSTN
SW_PWDN
PWRONB
CNT1
500 ns
Hosc_clk
stretch
II_RSTN
I_RSTN
FREEZE
(force gating of
HOSC clk)
CNT--
CNT=0
CNT=K
CNT=0
EN_SWPWDN /
EN_HWPWDN
HW_PWDN /
SW_PWDN
PWRONB
II_RSTN
HOSC_CLK_G
clr
load
FREEZE
CNT1
Under reset
Exec
Boot
CPU status
HOSC_CLK
HW_PWDN